Wikibon Energy Labs focuses on the energy consumption of IT equipment in the data centers. It works with vendors, utilities such as PG&E, and data center management to assess the power characteristics of IT equipment, and help vendors and IT organizations obtain incentive payments for green storage from power utilities.

As a result of this work, we have collected and managed a significant amount of data concerning power and storage in the data center. Figure 1 is a summary of the power costs of current generation storage arrays for different storage tiers. The power costs of tier 2 and 3 storage is 11% of yearly costs comprised of hardware, software and maintenance. Including tier 1 storage in the mix, the overall cost of power is $99/terabyte/year, or 9.5% of hardware, software and maintenance expense. The assumptions and the detailed calculations leading to the figures in Figure 1 are given in the footnotes in Figures 3 and 4.

Figure 1: Power Costs per TB for Current Storage Arrays by Storage Tier

It is also instructive to look at not just the latest current technology, but also at all the storage in the data center. Figure 2 takes the data for current technology and looks at the power consumption of all the storage in the data center. The overall conclusion is that the average cost of power for all storage in the data center is $196/TB/year and 14% of the hardware costs. However, the most striking conclusion from Figure 2 is that the cost of providing power arrays over 4 years old increases to over 4 times the cost of current equipment. When power together with maintenance is taken into account, equipment more than four years old is more expensive to maintain than replace with current storage array technologies.

Figure 2: Total Power Costs per TB by Year

So why is this not done? There are two major reasons that have been given by Wikibon members:

The cost of power is not a CIO budget line item

The cost of decommissioning an old array and migrating the data to new arrays is expensive (up to $50,000), takes a long elapsed time (1-5 months including planning), is disruptive to applications and risky unless skilled (and therefore scarce) resources are used.

As a result, the average age of storage arrays in the data center is 4.7 years, and 45% of the arrays installed in the average data center are over 4 years old. This is not sustainable unless energy costs plummet.

Action Item: Storage arrays over 4 years old are costly to maintain and a green disaster. The best high-end solutions are the recent announcements of clustered storage arrays from EMC and Hitachi, which promise to allow non-disruptive storage migration "forever" in 4Q 2009. Compellent may be looking to join this group with an upcoming release of a feature called "Live Volume". The use of heterogeneous virtualization technologies such as IBM’s SVC, LSI’s SVM and Hitachi’s USP V can also help to migrate data from old arrays to new arrays with minimal effort. An appliance offering from FalconStor also offers a potential solution. IT senior management should build in the cost of decommissioning storage arrays into the business case for new storage, and actively decommission storage arrays older than four years from the storage infrastructure.

Footnotes: The detailed assumptions and calculations behind the data in Figures 1 and 2 above are given in Figures 3 and 4 below: